Numerical modelling of carbon fibre-reinforced polymer and hybrid reinforced concrete beams in fire Muhammad Masood Rafi 1, * ,† and Ali Nadjai 2 1 Department of Earthquake Engineering, NED University of Engineering & Technology, Karachi 75270, Pakistan 2 FireSERT, University of Ulster at Jordanstown, Shore Road, Newtownabbey, BT37 0QB, UK ABSTRACT Investigation on the fire resistance of fibre-reinforced polymer (FRP) reinforced concrete (RC) is essential for increased application of FRP bars in the construction industry. Experimental tests for determining the fire resistance of RC elements tend to be expensive and time-consuming. Although numerical models provide an effective alternative to these tests, their use in case of FRP RC structures is hindered because of the insuf- ficient constitutive laws for FRP bars at elevated temperatures. This paper presents the details of a numerical modelling work that was carried out for simply supported carbon FRP (CFRP) and hybrid (steel-FRP) bar RC beams at elevated temperatures. Constitutive laws for determining temperature-dependent strength and stiffness properties of CFRP bars are proposed. Numerical models based on finite element modelling were employed for the rational analysis of beams using the proposed constitutive laws. The behaviour of concrete was simulated by means of a smeared crack model based on the tangent stiffness solution algo- rithm. The employed numerical models were validated against previous experimental results. The theoretical rebar stresses were calculated in both the FRP and steel bars, and the differences are discussed. Copyright © 2012 John Wiley & Sons, Ltd. Received 12 November 2011; Revised 27 February 2012; Accepted 15 March 2012 KEY WORDS: fibre-reinforced polymer; fire resistance; concrete beams; deflection; temperature distribution; numerical analysis; stiffness 1. INTRODUCTION Fibre-reinforced polymers (FRPs) are made of innovative non-corrosive materials, and the use of FRP bars in reinforced concrete (RC) structures can reduce durability problems associated with steel RC. Investigation on the fire resistance of FRP RC is essential for widespread application of FRP bars in different civil engineering structures. Generally, two approaches are employed to carry out such investigations. In the first approach, fire resistance tests are carried out on full-scale specimens to assess their suitability during fire; however, fire tests on RC elements are not only expensive but also time-consuming, owing to the time required by concrete to reach a stable moisture condition. An alternative to these tests are calculation methods, based on the results of fire resistance tests on common structural members; these methods can be used to develop analytical procedures, which can be employed as an alternative to experimental tests. The rapid development in the modern computing technology for the last 20 years has permitted the professionals to solve complex engineering problems using sophisticated analytical and numerical techniques. The use of finite element modelling (FEM) in the analysis and design of RC structures is one of these techniques. FE models can be employed for determining and monitoring structural *Correspondence to: Muhammad Masood Rafi, Department of Earthquake Engineering, NED University of Engineering & Technology, Karachi-75270, Pakistan. † E-mail: rafi-m@neduet.edu.pk Copyright © 2012 John Wiley & Sons, Ltd. FIRE AND MATERIALS Fire Mater. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fam.2135